1. Field of the Invention
The present invention relates to an end separating device for a sheet having a backing paper and, more particularly, to an end separating device for a sheet comprising a film and a backing paper superposed with respect to one another through an adhesive layer, wherein the backing paper is to be separated from the film at an end portion of the sheet so that the entire backing paper may be easily separated for use of the sheet.
2. Description of Related Art
Widely used in various fields is a sheet made by forming an adhesive layer on one surface of a film and attaching a backing paper to the adhesive layer. In general, such a sheet is used in such a manner that the backing paper is separated from the film at an end portion of the sheet with fingers or the like, and then, the film thus separated is to be attached to various kinds of medium. Such a sheet is disclosed in U.S. Pat. No. 4,927,278, for example.
As a measure for easily separating the backing paper from the film of such a sheet, it is known that the film only is cut at a suitable position of the sheet to effect half cutting of the sheet. In using such a half-cut sheet, the sheet is bent at the cut portion and the film is then separated from the backing paper. Such a half-cut sheet is disclosed in U.S. Pat. No. 5,066,152 (corresponding to European Patent Publication No. 0319209), for example.
However, according to the former separating method such that the backing paper is separated from the film at the end portion of the sheet with fingers or the like, it is difficult to separate the backing paper from the film with the fingers because the film and the backing paper are closely attached to each other through the adhesive layer even at the end portion of the sheet. Further, there is a possibility that the end portion of the sheet is bent in the course of repetition of a separating operation, rendering the separation of the backing paper more difficult.
On the other hand, according to the latter separating method such that the half-cut sheet is used, the film can be easily separated from the backing paper because the film only is previously cut. However, it is difficult to form a cut in the film only. Particularly when employing a thin backing paper, it is necessary to use high-precision parts in a half cutting mechanism for forming the cut in the film only, and it is also necessary to control assembly of such high-precision parts with high accuracy.
Accordingly, the use of such high-precision parts and the high-accuracy control of assembly of the parts cause an increase in cost. Further, there is a possibility that the backing paper is partially cut in spite of such high-accuracy control, with the result that the easy separation of the film from the backing paper cannot be attained.
Additionally, in the case of using the half-cut sheet mentioned above, a part of the film separated together with the backing paper is obliged to be wasted, causing an increase in running cost of the sheet.